Garden Pests and Treatments

The usual garden pests and their treatments:


Black ants do not sting but may bite; red ants sting. They are all attracted to the honeydew excreted by aphids. The black milk and move aphids to better feeding sites, and they overwinter aphids and eggs in their nests. They also effectively keep almost all predators away from their flocks! Ants may do the same for other pests such as scale insects, whitefly and mealy bugs. They may, however, prey on some other pests, and they may be pollinating plants unbeknown to us. For example, Chinese citrus growers have used them to control caterpillars.

garden pests and treatments Ants uproot seedlings and even large plants with their burrowing. The main problem is their arrival in the house or store. Strewing the mint family especially spearmint or pennyroyal will repel them. Growing mints or tansy near their entrance point will similarly help. Non-drying sticky bands are a very effective preventative barrier.

Nasty option: put out some sugar, watch where the ants take it home to, then pour boiling water down their hole.



Aphids are generally considered a plague, but often do little real harm. They do not suck sap, but allow it to be pumped through them, taking what they want and letting the sticky sweet sap residue fall on leaves where it turns mouldy. They can do serious damage by spreading virus diseases, but otherwise aphids are usually just taking surplus nutrients without affecting overall growth. The curling of leaves especially of tip growth has the same result as summer pruning —for many plants, redcurrants and sweet cherries in particular, withering the tips causes young buds lower down to convert to fruit buds instead of staying vegetative. There are many different aphids, some are specific to a few plants while others are less particular. Chives discourage aphids on many plants, nasturtiums although themselves attacked will keep broccoli clear.


Ladybirds and hoverflies

Ladybirds and hoverflies are the best control, so plant attractants like Limnanthes douglasii, buckwheat and Convolvulus tricolor. If these fail then soft soap works well. Traditional but now illegal was the use of plant extracts such as elder or rhubarb leaves combined with the soap. Never ever use detergent! Likewise, fumigating aphids with burning tobacco is no longer allowed. In the greenhouse, diseases, parasites and predators are all available to control aphids.


Flea beetles

Flea beetles make many tiny holes in the young leaves of plants especially turnip, radish and Chinese cabbage.

They dislike moist conditions, so frequent watering is most effective and usually only required while the seedlings are small. Interplanting lettuce or spinach deters them and they can be discouraged with mint, wormwood and elderberry leaves. Pieces of tomato plants are most effective. Sticky flypaper waved close overhead thins them out rapidly, as they jump up when disturbed.



Caterpillars are often not spotted till rather too late, but then it is worth hand picking or shaking them off on to a sheet. Sticky bands can stop them climbing back. For many, such as the cabbage white caterpillars, you may use a bacterial control, B. thuriengiensis, which rapidly stops their attacks. Surprisingly, nature will control caterpillars in time to prevent real damage; often the outer leaves of my brassicas are damaged, but the plant soon recovers.

Slugs and snails can be stopped by barriers of salt, lime, wood ashes, soot, pine needles, crushed eggshell or sawdust. They are reluctant to climb over smooth rings cut from plastic bottles. Slugs can be trapped in ‘slug pubs’ — saucers or yoghurt pots half full of fermenting jam and beer, in which slugs obligingly drown themselves. ‘Friendly’ ground beetles also drown unless you give them some twigs to climb out on.

slugs - garden pests and diseases


Slugs and snails

Slugs and snails also unwittingly congregate under tiles, melon or orange shells and upturned saucers from where they can be collected. Do not destroy the now rare predatory slug Testacella. It is yellowish with a small but noticeable vestigial shell on the tail. Many beetle species eat the mollusc’s eggs, some such as glowworms attack directly and Tachinid and Sciomyzid flies parasitise the adults. All of these thrive under moist groundcover. There is a parasitic nematode available you can water on to the soil to kill slugs and snails where they hide.


New Zealand flatworm

The New Zealand flatworm is a new pest in the UK mostly confined to the non-limey wetter west and north. It destroys true worms and damages fertility. It can be attracted to worms as bait and trapped in buried jam jars and in piles of flat tiles and under bricks etc.


Scale insects and mealy bugs

Scale are most troublesome on plants under cover and on walls. The little flat helmets hide an aphid-like pest which soon proliferates and they cunningly hide out of sight on the backs of leaves and branches. Naturally controlled by beetles, ladybirds, lacewings, and anthocorid bugs. Help build up numbers of the latter by planting willows, which produce an abundance of catkin pollen in early spring. Hand pick minor infestations, spray with soft soap or derris and buy in predators. Mealy bugs are very similar, but mobile, and can be treated with bought-in predators such as the beetle Cryptolaemus montrouzieri. The bugs are attracted to potato shoots, so can be trapped there, then sprayed with soft soap and derris.



Whitefly are mostly a problem under cover. They are unrelated to the pest of outdoor brassicas, though the same physical methods and sprays work for both. Thin out flying adults with a vacuum cleaner, use trap plants as suggested above and spray with soft soap. Indoors, introduce the commercially available biological control. Whitefly parasites Encarsia formosa are small wasps that rapidly reduce whitefly populations and have been used since the 1920s. The white scales turn black once attacked by the wasp. As these wasps fly when disturbed, infestations of aphids or other less mobile pests can still be controlled by dipping the tips of plants, where the pests concentrate, in soft soap solution. Remove yellow sticky traps from greenhouses once the wasps are introduced. Other predators are available. Out of doors, grow hops, as these breed up the Stethoras ladybird that attacks whitefly.


Spider mites

Spider mites are a serious threat to plants under cover, on walls and even in the open. They cover shoots with fine webbing that repels sprays and turn leaves yellow and desiccated with thousands of tiny pinpricks. Spraying water and keeping the air humid discourages them. Attract them onto plants of sweet tobacco which are then composted. Spray with soft soap and derris and introduce a biological control. The predators Phytoseulis persimilis are tiny, but still bigger than the pests and work very well if introduced early enough. Outdoors, many beneficial insects do the work for us, especially lacewings and ladybirds.



Wasps are very beneficial early in the season because they hunt other insects in great numbers, but when they turn to fruit they need trapping. A bottle half full of water and jam capped with foil and only a small hole allows the wasps to crawl in, but not to fly out. Do not use these near flowers or with honey as bees may also then be lured. Dusting wasps with flour enables you to follow them home. The nest can be destroyed by flooding or puffing derris dust in the entrance when they fly in at dusk carrying it in with them and repeated a week later.


Vine weevils

The adult weevil is dark grey, beetle-like with a very long snout and takes rounded bits out of leaves. However, most harm is done by the grubs, which have a grey-pink body and brown head and destroy the roots of many plants. Adults may be trapped in rolls of corrugated cardboard, bundles of sticks or under saucers, in which they hide during daytime. Vine weevils are very difficult to control with chemicals, as the troublesome larval stage live in the soil or compost, but there is a parasitic nematode you merely water on that controls them. For vines and plants in pots make an excluding lid that fits snugly around the stem or stand them in double saucers with a water moat between. Outdoors, vine weevils are controlled by trapping, clean cultivation — and very effectively by keeping chickens.


Eelworms or nematodes

The larger saprophytic varieties are mostly harmless — the nematodes that are pests are too small to see, though they may cause damage that can be seen. On potatoes they form visible cysts on the roots. Many fungi attack eelworms, so organic soils rich with compost suffer much less. Tagetes marigolds give off secretions that kill nematodes and can be planted to clean the ground. Crotalaria, castor oil plants and pot marigolds (Calendula officinalis), may-discourage them. Some are themselves parasites of other pests.



Only netting the area will keep rabbits out. In case they get in, have a plank ramped against the fence so they are not trapped inside and eat even more. If the perimeter cannot be secured, surround or wrap each plant in wire netting. If this is impossible feed the rabbits when snow stops them finding their own food and before they remove the bark from your plants! Just the smell of a ferret or its droppings will drive them away. Humane traps work! Moles Countless suggestions have been made to deter moles, but none has ever proved consistently efficacious — find one that always works and you will have fame and fortune. Try euphorbias, Incarvillea and castor oil plants if you must, but only if you like irritant and poisonous plants. Poke sharp, twiggy, thorny things down their holes, flood them, gas them with car exhaust, pour foul, disgusting things down their runs. You will only discourage them for a while or drive them to the neighbours temporarily! Why not accept them and appreciate the pest control, ventilation and fine soil they leave? Some dogs and cats can be taught to catch moles.


Two-legged rats

These can be the worst pests of all and their senseless damage is worse than their thefts. Fences, barriers and locks are sadly now required especially for succulent fruit. Signs saying ‘Beware of the wasps nests!’ can be singularly more effective than ‘Keep out’. Dogs are considered the best guards, but geese are as good and have other benefits.


25. January 2011 by admin
Categories: Featured, Pest and Disease Control | Tags: , | Comments Off on Garden Pests and Treatments


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